Because reasoning allows us to justify our beliefs and evaluate these justifications it is central to folk epistemology. Following Sperber, and contrary to classical views, it will be argued that reasoning evolved not to complement individual cognition but as an argumentative device. This hypothesis is more consistent with the prevalence of the confirmation and disconfirmation biases. It will be suggested that these biases render the individual use of reasoning hazardous, but that when reasoning is used in its natural, argumentative, context they can represent a smart way to divide labor without loosing epistemic value